1. Field of the Invention
The present invention relates to an electric surgical high-frequency instrument having an HF (high frequency) source to which an inactive electrode for tissue contact and an active electrode for surgical treatment can be connected via electrical conductors. More particularly, the present invention relates to such an instrument which includes an antifaradization capacitor in the electrical conductor of the active electrode and which also includes a control circuit for sensing a direct current component in the HF circuit which is connected to at least one of the electrodes and which furnishes an output signal for controlling the HF source.
2. Brief Description of the Relevant Art
One such known electric surgical high-frequency instrument (DE-PS 28 01 833) is connected to a variable souce of HF current with an inactive electrode for tissue contact and an active electrode for tissue cutting via an antifaradization capacitor. The binding posts of the antifaradization capacitor are connected to corresponding inputs of an amplifier furnishing a voltage signal to an input of a differential circuit, the other input receiving a reference voltage. The differential voltage generates a control signal for the source of HF current depending on the applied voltages.
Tests on such an instrument have shown that the voltage sensed at the antifaradization capacitor is not suitable to generate a signal for satisfactory control of the HF source and thus for control of the electric arc necessary for cutting.